Like most Americans, I know nothing about international holidays that don't predate the Founding. However, the friends I made in Israel two Decembers ago have pointed out to me that today is International Holocaust Remembrance Day. I can see why they would consider it a matter of importance that we know of it.
My only advice about holocausts is that it's ordinary people who have to stop it. Governments are often behind them. If not governments, it's mobs that governments are too weak to stop. The right tools and training for the people are important. In the Rwandan Genocide of 1994, it was mostly machetes that killed all those people. They mostly had machetes to try to stop it. It might have worked, had they trained in how to use machetes together in defensive formations. Rifles would have worked better, even against men with rifles, especially if they had training as well as tools.
We may or may not see another such holiday without a new bloodletting on a similar scale. The pressures of the war in Syria have created millions of refugees. The war in Afghanistan is about to get much worse. The oil war between Iran and Saudi Arabia, made possible by Obama's Iran deal, is likely to destabilize whole regions -- including in Latin America. We've been brought to a dangerous moment by unwise leaders whose eyes are closed to their folly.
Semper paratus. Think on your moral duty, and rather die than yield it.